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NOV. 18 Re. F. DESEAUER ELECTR I CAL TRANSFORMER S YSTEM Original Filed July 23, 1918 3 Sheets-Sheet l E E lano a 6 a R E U A S S E D F ELECTRICAL TRANSFORMER SYSTEM Original Filed July 23 1918 i5 Sheets-Sheet 2 (Juucufo:

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F. DESSAUER ELECTRICAL TRANSFO RMER SYSTEM Original Filed July 23, 1918 3 Sheena-Sheet 5 (lawn to:

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Reiasued Nov. 18, 1924.

FRIEDRICH DESSAUER, OF FRANKFORT-ON-THE-MAIN, GERMANY.

ELECTRICAL TRANSFORMER. SYSTEM.

Original ll'o. 1,872,653, dated larch 22, 1921, Serial No. 246,405, filed July 23, 1818. Application for reissue filed March 21, 1928. Serial No. 626,708.

To all whom it may concern:

Be it known that I, Fnramuon DESSAUEB, a citizen of Germany, residing at Frankfort- -on-the-Main, in Germany, have invented a new and useful Electrical Transformer System, of which the following is a specification.- This invention relates to high tension transformer systems, one of its principal objects being to provide an improved arrangement of transformers, either for stepup or step-down transformation, which is lighter, cheaper, and more compact and has greater working security than those heretofore known. Another obj eot is to provide an im roved arrangement in which the potentia stresses throughout the system are distributed and controlled so that the quantity of insulation heretofore required may be greatl Y reduced. Still another object is to provi e a system of transformation which may be extended indefinitely to increase the voltage of the high tension circuit merel by the addition of transformer units wit out increasing the potential stresses in those units already installed. These and. other objects of the invention will be apparent in the annexed description and accompanying drawings, in which Figs. 1, 2 and 3 illustrate Various forms of known transformer systems.

Figs. 1" and 2* show the potential stresses between various parts of the systems shown in Figs. 1 and 2 respectively.

Fig. 4 shows a system arranged according to one form of my invention.

Fig. 4" represents the potential relations existing in the arrangement of Fig. 4.

Figs. 5 and 6 show the system of Fig. 4 extended to include additional transformation units.

Fig. 5 represents the potential relations existing in the arrangement of Fig. 5, and

Figs. 7, 8 and 9 illustrate modified forms of the invention.

Throughout the description I shall use the term high tension winding and low tension winding in the customary sense of windings between whose terminals there exists :1 relatively high and relatively low potential difference or voltage respectively. I shall use potential to mean absolute potential or potential with respect to the earth, except in cases expressly stated otherwise, and when the term potential is applied to coils or windings it means the maximum instantaneous potential existing in any turn of the winding.

In high tension transformers of a iven size, the electrical stresses *0 which the insulating layers are subject, and thus the danger that these layers be damaged or unctured, depends upon the potential diference existing between the sides of the layer. In transformers heretofore known 1t has been impossible to maintain this potential difference less than a certain limit, namely one-half of the voltage or potential difference between the ends of the high tens1on winding, and even this condition can be maintained only when the middle point of the high tension winding is grounded or maintained at earth potential. Thus in case the system is so arranged that the high tenslon winding of a given unit cannot be grounded or can only be grounded at one end, this potential difi'erence cannot by any means heretofore known he made smaller than the voltage of the high tension windmg.

For example, Figure 1 represents an ordinary high tension transformer having-a low tension winding w connected to an alternating current circuit m and having a core 2' and a high tension winding 8. Assume that the voltage of the secondary winding is 100 kilo-' volts. In Figure 1 the number of secondary turns of the winding 8 are plotted as abscissae and the potentials of the corresponding turns plotted as ordinates. If the end I; of the secondary winding is grounded the line all) represents the potentials of various portions of the winding. In this case there exists a maximum potential difference of one hundred kilovolts between the high tension winding on one hand. and the core and low tension winding on the other hand, which latter are usually at substantially earth I potential. If however the middle point m of the winding 8 is grounded the potentials of the various turns of the winding are shown by the line ab, and it will be seen that the maximum difference of potential existing between the core or primary winding and the adjacent turns of the secondary winding is 50 kliovolts or one-half the voltage of the secondary winding.

In Figure 2 two transformers T and T are connected with their high tension windings in series, the arrangement being other wise similar to that shown in Figure 1.

in this case if the conductor c by It has previously been proposed to distribute theinsulation stresses by interposing be-. tween the low tensionwinding and the external alternating current circuit one or more transformers which transmit energy in non-conductive relation. This arrangement is shown in Figure 3, wherein the low tension winding p of the transformer T is connected to the winding 1' of a transformer H which is preferabl -of a 1 to 1 ratio. The other winding w o the transformer -h is connected to the external circuit an. Even in this case the tential difference between the winding .9 an the core i or low tension windcannot be maintained less than one-half h f tlie potential of the secondary winding.

With the means heretofore known, we are, as'is pointed out in the foregoing, bound to deal with a minimum difference of potential (amounting to half the potential of the high tension winding) between those parts of the transforming arrangement which are most exposed to the danger of being damaged. In consequence, the insulating parts of the arrangement must be constructed to withstand that difference of potential. This drawback is so much the more serious, as the-insulating parts in transformers are strained tothe utmost by the high voltages which are in use at present in certain a plications of transformers, such as in hig voltage testing apparatus or in Roentgen-ra apparatus for the treatment of diseases. oreover it is to be (1 that it will become desirable to use still hi her voltages in these applications as we as in high tension work in general. A voltage of more than 100000 volts requires cumbersome and expensive transformers to fulfill the necessary working conditions.

The essential progress brought about by my invention is that the heretofore unvariable relation between the secondary voltage and the strain of the dielectric in transformers ma be controlled. The maximum potential difierence between the secondary and other parts of a transformer is not limited to at least the half of the secondary voltage; it may be diminished at will. Correspondingly the difierence of potential between the second and an part of the transformer may be I will now describe in detail by way of example a number of embodiments of my invention. V

Figure 4 shows two transformers T and 'consumin T, the high tension a a, of

which are connected in series. e low tension windings p and p, of these transformers are connecte across the windings 1- and 1', respectively of the transformers H,, H? the ratio of transformation of which is p erably but not' necessarily 1 to 1. The purpose of H and H, is to oin the low tension windings p and p, in energy transmitting relation withanexternal alternating current circuit 2, which may be either a generating or 'circui and at the same time to insulate e windings p, and from each ,other and from this circuit. e int of junction 0 of the high tension windings a, and s, is grounded. Therefore at an assumed l'r tension voltage of 100 kilovolts between e terminals a and b the tential of either a or b is kilovolts. erefore the middle ints d and e of the transformers T and are at a otential of 25 kilovolts. The points (1 an e are connected respectively to the core i, and low tension winding]; and the core 2', and low tension winding 1),. Therefore the maximum difference of potential between the secondary win and an adjacent part of the correspon trans ormers is onl 25 kilovolts. This relation is shown aphically in Fi ure 4 in which the num r of turns of tfie secondary winding are lotted as abscissa against the potentials o the terms as ordmates. The potentials of the various elements of the system are indicated by the letters a, p, r, 1, etc., with appropriate subscripts. Thus the maximum difierence of potential between any two adjacent groups of conductors in this system is limited to one quarter of the voltage of the high tension' circuit, that is the electrical strain in the system is a quarter of what it would otherwise be.- It is true that the tr formers H and H, have to sustain a tential difference of 25 kilovolts between t eir primary and secondary windings but this requirement is easily met as these transformers are usually small and both windings have equal numbersof turns. In this discussion it is assumed that the potential of the windings w 'w, is that of the earth since the actual potential of these windings will in practice he in the neighborhood of 200 volts, an amount which is n ligible in com-- parison with the volta e oft e high tension circuit which may be om to 300 kilovolts.

Since the hi h tension windings a, and s, are connec in series it is obvious that a single winding may be used instead of these two. Therefore the essential feature of this modification of the invention is that at least three windings cooperatin to produce a high tension current are use (namely the single winding 8,, a, and the two windings p 1),) and that at least two of these windings (namely 12, and 1),) are placed in a'separate branch of energy transmission, each branch of energy transmission being designated by separate transformers H and It will be seen that these branches permit the transmission of energy in non-conductive relation and keep the low tension winding 1), p insulated from each other and from the external circuit 2:.

Since the stress upon the insulation of the high tension transformers is so materially reduced, a much smaller quantity of insulation is required, and conseguently the price of these transformers is re uced more than enough to compensate the additional cost of the transformers H, and H The net cost of thesystem is thus materially lessened. Moreover due to the reduction of the potential stresses between the adjacent points the working security of the system is greatly increased and I wholly avoid loss of energy by the henomenon of silent or glow discharge winch is well known in high tension work and which frequently attains considerable amounts.

Figure 5 illustrates the modification of Figure 4 extended to include three high tension transformation units T T T which have their high tension windings s 8 a, connected in series. In this case the middle point r: of the high tension circuit is grounded, the potentials of the points a, I), fl and (a being indicated by way of example in the drawing. The potentia s of the various parts of the system are indicated graphically in Figure 5. Assume a potential difl'erence or voltage of 140 kilovolts between the terminals a and 7) of the high tension circuit, the potential of the points a and b is then 70 kilovolts and the potential of the point (I and e is kilovolts. The low' tension windings and p, are linked to the external circuit a through auxiliary transformers H, and H. as in Figure 4, the low tension winding 72 being connected in series with the low tension windings 1n, and 10,. The low tension windings p, and 7) are connected to the cores i, and i and to the points (i and 6 respectively, which latter are at a potential of kilovolts. These cores and windings are therefore maintained at 35 kilovolts and the maximum potential difference between them and their adjacent high tension windings is kilovolts minus 35 kilovolts or 35 kilovolts. In this case the auxiliary transformers H and H are insulated to withstand 35 kilovolts and the potential difference between any two adjacent conductors in the system cannot be more than 35 kilovolts or one fourth of the voltage of the system.

Figure 6 shows the system of Figures 4 and 5 extended to include 5 high tension transformation units producing a voltage of 210 kilovolts. This .extension is effected the other units T T, T and T,

is assumed to have a voltage of 35 kilovolts? Thus with the middle point of the system c grounded the total voltage of the high tension circuit is 210 kilovolts and the potentials of the points between the various high tension windings are 35 kilovolts and 70 kilovolts as indicated in Fi re 6. The low tension windings 7), an and the cores 2', and z, are now connected to points whose potential is 70 kilovolts and the transformers H and H as before are made to withstand 35 kilovolts. The low tension windings p and p, are connected to the cores 2', and i and to points in the high tension system whose potential is 35 kilo volts. The windings p, and p are likewise connected across the windings v, and a, of the transformers G and G which are Figure 5 and connected in series with the windings w,

H and H and w, and '0 and '0 are thus maintained at an absolute potential of 35 kilovolts. The transformers Gr and G are likewise made to withstand a potential of 35 kilovolts and can thus be connected between the external circuit a: and the auxiliary transforniers H and H the windings r, and 1', of which are at a potential of 70 kilm'olts.

Obviously, any one of the arrangements of Figs. 4, 5 and 6 can easily be formed out of its precedents (e. g. Fig. 6 out of Fig. 5, 4 or 1), merely by adding transformers. This is an important advantage of my system-viz, I am enabled, by my system, to adapt, by the mere addition of transformers, a given alternating current supply apparatus to a higher range of voltage, and nevertheless to make use of all the parts of the given apparatus as before. Preferably. I avail myself of standardized types of additional transformers (especially in the form of 1:1 transformers), their manufacture and repair being sim le.

As is demonstrated by ig. 7, I may modify my system, so as to allow the tential of any of the several on s of conductors to be regulated at will. 11 Fig. -7, the middle J (e) of the high tension windings a, (a 7 of eachof the two high tension transformers T and T is connected to the ground by a series of condensers f, and anothelr connection is made between the circuit of t 10 respective prima windin 1 and a point h in the set d f condengerz.

and w of the transformers 'lhe windings w,

. Fig. 8.

cording as I choose that point of connection It, I obtain,

of the high tension winding on one hand, the ground on the other hand, any des1red potent1al of the low tension winding p, (p and Iron wre i, (1 Instead of a 531188 of conas in Fig.7, I may make use of an adjusts le resistance to efiect the desired tential. In some cases'I find it advisa le to. regulate the potential of the various ups of conductorsby connections to in ependent sources of energy, instead of deriving their electrical charge from the corresponding high tension transformer in the system.

As already mentioned, not only transformers but any device capable of transmitting electrical energy without a conductive relation between its ener transmitting parts, as, for instance, con ensers, may

be used to produce the separation of the ups of conductors and therefore to enable t eir levels of potential to be ad'usted. This form of my system is exemp by Fig. 8 is in accordance with Fig. 4 exce t that the place of the transformers H, and H, of Fig. 4 is taken by condensers k.

The artificial adjustment of the potential of the groups of conductors, according to invention may be advantageously applied even to cases in which the maximum difierence of potential between the hi h tension winding and the othereparts of t e same transformer need not he need to less than one half of the secondary voltage. In the case, for example, of a bi h tension transformer having one end 0 its high tension windin flgrounded for any reason, the maximum erence of potential acting upon the insulating layers of arrangements heretofore known, amounts, as is stated above, to the total secondary voltzfie of the transformer, and cannot be redu by any means heretofore devised. B inserting an intermediate circuit, the love of potential of which is made adjustable, according to m invention, I reduce the strain of the insulating layers to one half of what it unavoidably amounted to in the heretofore known transformers with one end 'of the high tension winding grounded. This is demonstrated b Fig. 9 which shows an arr ment sim' at to that of Fig. 3. As already stated in connection with F' 3, it is impossible to reduce the strain 0 the insulating layers by a mere re transformation. If, however, the intermediate circuit Z and iron core 1' is, as in Fig. 9, connected to the middle 0 of the high tension winding 8, or otherwise ke t on a level of tential situated between t e potentials of o ends a and b of a on one hand and of we: on the other hand,

the su ply circuit be reduced to a half,

then strain can I within the limits of the potential of the middle even if one end (12) of the high tension winding 8 is in connection with the ground g.

In many cases, I have found, that the connection between the iron coresand windings, as shown in Figs. 4-9, may as well be omitted, as the iron cores, being embedded between the coils, usually adopt automatically an average level of potential as compared with the surrounding. coils.

It is to be understood that the invention is not limited to the particular details described for the sake of illustration but includes modifications which fall within the scope of the appended claims. For instance, the system is equally well adapted to stepup and step-down transformation. Furthermore I have described the high tension windings as connected directly in series, but the term connected so that their voltages are accumulative is intended to include any connection of the hi h tension windings so that the voltages o the individual windings add, whether the windings are connected directly to each. other or linked in series by means of intermediate windings or other up aratus.

Having t us described the invention what is claimed as new and desired to be secured by Letters Patent is:

1. In a high tension transformer system, in combination, a pluralit of transformers having high tension and ow tension windings, the transformers being so connected that the voltagesof the high tension windin are cumulative, and means for maintaming the low tension winding? at desired potentials with respect to the igh tension windings. V

2. In a high tension transformer system, in combination, a lurality of transformers each having a high tensionswinding, a low tension winding, and a core, the transformer being so connected that the voltages of the high tension windings are cumulative,

and means for maintainin the low tension windings and the cores at esired potentials with respect to the high tension windings.

3. In a high tension transformer system,

in combination, a plurality of high tension transformers each havin a high tension winding and a low tension winding, the transformers being so connected that the vol of the high tension windings are cumu ative, and means for maintaining the maximum potential difierenoe between the high tension windings and all other [conductive partsof the respective transformers tension windin and a core,the transformers so that the voltage of the being connec IOU high tension windings are cumulative, and connections between the respective cores and high tension windings at points in the high tension circuit whose potentials to earth are less than the maximum potentials of the respective high tension windings.

5. In a high tension transformer system, in combination, a plurality of transformers each having ahigh tension winding and alow tension winding, the transformers being so connected that the voltage of thehigh tension windings are cumulative, and connections between the respective low tension and high tension windings at points in the high tension circuit whose potentials to earth are less than the maximum potentials of the respective high tension windings.

6. In a high tension transformer system, in combination, a plurality of transformers having high and low tension windings, the high tension windings being connected in series, an external alternating current circuit, means for linking the low tension windings to said circuit in energy-transmitting relation, and means for maintainin the low tension windings at desired potentials with respect to the high tension windings.

7. In a high tension transformer system, in combination, a pluralityof transformers each having a high tension winding and a low tension winding, the high tension windings being connected in series, an external alternating current circuit, means for linking the low tension windings with said circiut in energy transmitting relation and for insulating the circuit therefrom and means for maintaining the low tension windings at a potential different from that of the circuit.

8. In a high tension transformer system, in combination, a plurality of transformers having hi h tension and low tension windings, the igh tension windings being connected in series, an external alternating current circuit, means comprising auxiliary transformers for linking the low tension windings with the circuit and insulating the circuit therefrom and means for maintaining the low ,tension windings at a potential different from that'of the circuit.

9. In a high tension transformer system, in combination, a plurality of transformers having high and low tension windings, the

high tension windings being connected in series, an external alternating current circuit, means for linking the low tension windings with said circuit in energy transmitting relation, and connections between the low tension windings and their correspondin high tension windings at points in the higi tension circuit whose potentials to earth are less than the maximum potentials of the respective hi h tension windings.

10. In a igh tension transformer system, in combination, a transformer having a high tension and a low tension winding, means connecting said windings at a point whose potential to earth is equal to or greater than the maximum potential difference in said windings, an external alternating current circuit, and means for linking the low tension winding to the circuit in energy transmitting relation and for insulating the low tension winding therefrom.

11. In a high tension transformer system, in combination, a transformer-having a high tension and a low tension winding, means for linking the low tension winding with an external alternating current circuit, said means having energy-transmitting parts in non-conductive relation, and means for maintaining a smaller potential difference between the low tension.an'd high tension winding than that existing between the high tension winding and the ground.

12. In a high tension transformer system, in combination, one or more transformers each having a high tension and a low tension winding, means for linking the low tension windings with an external alternating current circuit, and connecting means between the respective lo'w tension and high tension windings at points in the high tension circuit whose potentials to earth are equal to or greater than the maximum potential difference between the respective high tension and low tension windings.

13. In a high tension transformer system. in combination, one or more transformers each having a high tension and a low tension winding, one or more auxiliary transformers having an approximate one to one ratio of transformation for linking the low tension winding with an external alternating cur-- rent circuit, and connecting means between the respective high tension and low tension windings at points in the high tension circuit whose potentials to earth are equal to or greater than the maximum potential difference between the respective high tension and low tension windings.

14. In a high tension transformer system, in combination, three or more windings cooperating to produce a high tension current, two or more branches of energy transmission, each branch including one of said windings and one or more auxiliary tran'sformers, each of said windings which is included in the branches of energy transmission-being connected to a point in the high tension circuit between which and. the ground there exists a potential difference equal to or greater than the maximum potential difference existing between adjacent windings.

15. In a high tension transformer system, in combination, three or more windings cooperating to produce a high tension current, two or more branches of energy transmission, each branch including one of said windings and one or more auxiliary transincluded in the branches of ener formers, each of said windings which is transmission being connected to a point in the hi h tension circuit between which and t e ground there exists a' potential difl'erence equal to or greater than the maximum potential difierence existing between adjacent windings, said auxiliary transformers having an approximate one to one ratio oftransmission.

i 16. In a high tension transformer system, in combination, a transformer having high and low tension windin devices for linking the low tension win sai nat-ing current circuit, devices having with the alter energy transmitting partsin non-conduc tive relation, and means for maintaining a smaller difierence of otential between the conductive parts of the transformer adjacent to each other than that existin between the high tension winding an the ground.

In testimony whereof I hereunto aflix my signature.

DR. FRIEDRICH DE'SSAUER.

Witnesses: M

GEBHARD Hr'innns,

Joann Knacn'r. 

